Method for reducing fiber density and expanding face dimensions of self-supporting sheet structures



NOV. 17, 1970 p COLE 354,95

METHOD FOR REDUCING FIBER DENSITY AND EXPANDING FACE DIMENSIONS OF SELF-SUPPORTING SHEET STRUCTURES Filed Jan. 15, 1967 4 Sheets-Sheet 1 INVENTOR PAUL MORRISON COLE BY WW AGENT NOV. 17, 1970 p, COLE 3,549,

METHOD FOR REDUCING FIBER DENSITY EXPANDING FACE DIMENSIONS OF SELF-SUPPORTING S E T STRUCTURE Filed Jan. 15, 1967 4 She -Sheet 2 INVENTOR L 33 3| PAUL MORRISON COLE AG E NT NOV. 17, 1970 CQLE 3,540,958

METHOD FOR REDUCING FIBER DENSITY AND EXPANDING FACE DIMENSIONS OF SELF-SUPPORTING SHEET STRUCTURES Filed Jan. 15, 1967 4 Sheets-Sheet 5 l5 l4 J A M y 3 (A M DIRECTION H [2 OF TRAVEL 35 INVENTOR PAUL MORRISON COLE AGENT NOV. 17, 1970 p, MCQLE 3,54 METHOD FOR REDUCING FIBER DENSITY AND EXPANDING FACE DIMENSIONS OF SELF-SUPPORTING SHEET STRUCTURES Filed Jan. 13, 1967 4 Sheets-Sheet 4 4 INVENTOR PAUL MORRISON COLE MGM/am) AGENT United States Patent 3,540,958 METHOD FOR REDUCING FIBER DENSITY AND EXPANDING FACE DIMENSIONS OF SELF-SUP- PORTING SHEET STRUCTURES Paul Morrison Cole, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 13, 1967, Ser. No. 609,123 Int. Cl. B32b 31/08 US. Cl. 156-164 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method for treating self- A supporting sheet structures, and more particularly to a method for reducing the fiber density and expanding the face dimensions of such sheet structures.

U.S Pat. 3,085,922 issued Apr. 16, 1963, to C. R. Koller describes porous, flexible, self-supporting sheet structures composed of substantially parallelized, crimped, synthetic organic, polymeric fibers that are attached, e.g. by a binder composition, at a plurality of contact points throughout the three dimensions of the sheet. These selfsupporting fiber-on-end structures, as they will be referred to herein, can be used per se or in combination with a variety of backing layers to yield pile articles such as blankets, carpeting fabric interlinings, velvets, suedes, artificial furs, and the like.

Pile articles comprising the sheet structures of the Koller patent are especially unique because excellent functional and aesthetic properties are afforded even though the fiber density of the pile layer is quite low compared to conventional woven pile fabrics. In the case of carpeting, for example, a self-supporting fiber-on-end structure which has been laminated to a backing will noramlly exhibit a high degree of covering power and bulk, excellent compressional properties such as thickness recovery and load support, and yet contain in the pile layer only a fraction of the fiber weight that would be typical for a tufted carpet construction.

As a matter of economics, however, it has been found that the high bulk-low density properties of the fiber-onend sheet structures frequently pose a definite problem in the transportation of these structures from one geographical location to another. In certain instances it would be impractical to have the sheet structures manufactured in one area and shipped to another eg to a fabric convertor for lamination of the sheet to a backing, since the transporation costs would be prohibitive. In this regard an advantage of the process of the present invention is that a self-supporting fiber-on-end structure can now be manufactured in a comparatively dense low-bulk form, be shipped in that form from one area to another, and be subsequently bulked and expanded to a low density structure exhibiting the desired properties.

The present invention also enables greater versatility in the manufacture of the self-supporting fiber-on-end structures of the Koller patent, particularly from the standpoint of achieving structures having a low fiber density. Thus for certain techniques leading to these structures it heretofore has been necessary on occasion to use a quantity of fiber in excess of that required for the desired ice functional and aesthetic properties. For example, when immersing an unbonded assembly of generally parallelized fibers in a liquid binder composition to create fiber-tofiber attachments, the fibers must be closely packed or otherwise the weight of the liquid may cause the structure to collapse. By virtue of the present invention, a selfsupporting fiber-on-end structure can be advantageously formed with closely packed fibers and then be subsequently bulked and expanded to reduce the fiber density.

STATEMENT OF THE INVENTION In accordance with the present invention a method is provided for reducing the fiber density and expanding the face dimensions of a porous flexible, self-supporting sheet composed of substantially parallelized, crimped, synthetic organic, polymeric fibers which are attached at a plurality of contact points throughout the three dimensions of the sheet, the faces of the sheet preferably being composed essentially of fiber ends and the air within the sheet constituting at least about 50% of its volume. The method comprises a series of steps including, first, causing the sheet to engage the projections of a layer of card clothing so that the projections extend into the sheet. In a preferred embodiment wherein the faces of the sheet are composed of fiber ends the projections into the sheet are in general alignment with said fibers. Subsequently the layer of card clothing is flexed to spread apart the projections and thereby expand the face dimensions of the sheet. Then the sheet is set in the expanded condition to maintain a reduced fiber density in the sheet and the card clothing is removed therefrom. In a typical embodiment of the invention the card clothing comprises a multitude of closely spaced wires projecting from a flexible support layer. The Wires advantageously will extend through at least onefourth the thickness dimension of the sheet and will be provided at a density of at least 300 per square inch.

The so-called setting of the fibers in the expanded condition can be effected in a variety of ways depending upon the type of product to be produced and/or upon the nature of the fiber-to-fiber attachments in the initial structure. In a preferred embodiment of the invention the setting is performed concomitantly with the lamination of the structure to a backing material.

The invention is based upon the finding that a selfsupporting fiber-on-end structure can be caused to uniformly expand in its major dimensions, usually with little or no change in thickness, by controlled flexing or bending of the structure as it is internally reinforced by a multitude of projections extending from a support layer. The projections, by extending a substantial distance into the thickness of the sheet, serve to maintain to a coinsiderable extent the general alignment of the fibers during the flexing step but at the same time enable a uniform increase in the spacing between fibers or fiber portions. An essentially constant stress is placed upon individual fibers throughout the flexed portion of the sheet and as a result any tendency to form highly stressed weak spots or gross voids, as would be the case with ordinary stretching techniques, will be virtually eliminated.

In a preferred form of the invention, the process is operated on a continuous or at least semi-continuous basis. Several embodiments of such operations will be illustrated schematically with reference to FIGS. 1, 2, 3, 4, 5, 5a, 6, and 7 of the drawings. In each such arrangement the sheet is first contacted with the projections of a layer of card clothing and these are caused to become embedded to a predetermined distance Within the sheet. The card clothing is then caused to traverse an arcuate path, e.g. by rotation about a roll or drum, so that the projections diverge and become spread apart in at least the direction of the path and the dimensions of the sheet faces accordingly increase. The expanded sheet is then adhered to a backing to produce the desired pile artcile.

It will be understood that for purposes of this invention the so-called card-clothing includes commerical forms of wire clothing, e.g. as used in textile carding operations, as well as a variety of other analogous arrangements. It is only necessary that the card clothing include a flexible support layer, i.e. to facilitate bending through an arcuate path or radius, and a multitude of elongated projecting elements extending therefrom. The projecting elements should be generally uniformly distributed upon the support and should be relatively closely spaced, preferably at a density to provide at least 300 points per square inch, 46.5 points per square cm. In general the higher the density of the elements, the more uniform is the expansion. Individual projecting elements mounted upon the support layer may have a single point to engage the sheet or, when constructed like common wire staples, have two sheet engaging points. The projecting elements preferably comprise fine metal wires since these can be closely spaced to afford maximum reinforcement. The tips of the wires preferably are ground to sharp points, free of burrs, as is conventional in textile practice. The elements may also, however, be formed of plastic, ceramic glass or other materials and may have other cross-sections and elongated shapes as well. One suitable form of card clothing for use herein is a cloth backing having a maximum wire density (i.e., a maximum number of wires per unit areatypically 720 wire points per square inch (112 points per square cm.) of support surface) wherein each wire is approximately 0.010 inch (0.025 cm.) in diameter.

If during a flexing step about a roll the wires or other projecting elements of the card clothing fully penetrate the thickness of the self-supporting fiber-on-end sheet, then the sheet can be expanded almost exclusively in the longitudinal direction, and the transverse and thickness dimensions thereof will remain substantially unchanged. However, the depth of penetration may also be adjusted to permit the wires to penetrate only a small proportion of the total thickness of the sheet. In this case the sheet will expanded longitudinally, the transverse dimension of the sheet will remain subsantially unchanged, and the sheet thickness will become lower. For most purposes the projections should generally uniformly penetrate the sheet to a predetermined depth of at least about onefourth the sheet thickness. In applications where retention of the sheet thickness is especially desired, the projections should extend at least half-way therethrough. It will also be understood that the more the sheet is to be expanded longitudinally, the deeper the wires must penetrate towards the full thickness of the sheet. Longitudinal expansions in excess of 100% have been accomplished with fiber-on-end sheets in accordance with the invention without contraction in the transverse direction of the sheet and without any apparent reduction in the sheet thickness. By expanding the area of sheet as little as 20% or less, substantial economics can usually be realized.

In the case of card wire clothing, the wires may advantageously extend from the flexible support layer in such a manner as to intersect the sheet at an acute angle. For this purpose the individual wires may have an abrupt bend at a location which is distant from the tip. A preferred arrangement is shown in detail in FIG. 4, wherein it will be noted that the wires 10, aflixed to flexible support layer 11 of the card clothing 12, are uniformly inclined at angle A with respect to the face of sheet 13.

The generally parallelized fibers 14, bonded together by binder composition 15, extend mainly from one sheet face to the other. The wires are in general alignment with the fibers, i.e. extend from one face in the direction of the other. It will be noted in FIG. 4 that the wires are inclined in a direction opposite to the direction of travel of the card clothing during the operation of the process. This acute angle A, at which all the wires should preferably be inclined, may vary between 45 up to and including It has been found that by having the wires positioned to intersect the sheet surface at an acute angle A, the processing is facilitated, especially because the sheet can be more easily separated from the wire clothing after expansion. Properly angled wires are of particular benefit in that they enable the process to be operated in such a manner that the wires will move very little relative to the surface fibers at the sheet face during engagement and disengagement with the sheet. Thus when a fiber-on-end sheet is caused to tangentially contact a layer of card clothing which is passing about a roll, straight wires upstanding from the card clothing support layer will tend to be longitudinally pulled through the sheet as they become embedded in the sheet. This can cause distortion of the fibrous configuration even to the point where large voids or tears are created in the sheet. By having the wires inclined at a suitably selected angle which is opposite to the direction of travel, it is possible to virtually eliminate relative movement between the wires and the sheet surface and thereby encounter less distortion at that surface.

Although the invention has been particularly described with reference to the use of rotating rolls or drums to provide an arcuate path for the card clothing during the flexing step, other means for accomplishing the flexing will be apparent. It will be understood that some degree of lateral expansion can simultaneously be effected if, for example, the roll is in the nature of an ellipsoid as opposed to having a surface shaped like a right circular cylinder. Regardless of the means employed to effect the flexing, it will be apparent that the degree of curvature of the arcuate path will govern to a large extent the amount of expansion which takes place. The process of the invention can be operated with fiber-onend sheet materials of various dimensions including essentially continuous length material.

A full description of the self-supporting fiber-on-end structures and various methods for their production is set forth in the aforementioned Koller patent, the disclosure of which is incorporated herein by reference. Although a description of these structures, including definitions of the terms used in connection therewith, is fully set forth in the above Koller application, they will be briefly mentioned herein.

By crimped, alternatively contorted, it is meant that the profile (i.e. side elevation) of an individual fiber is irregular (i.e. not straight) when the fiber is viewed from at least one side. By substantially parallelized, it is meant that although the fibers are crimped, the mean axes of individual fibers are substantially parallelized, i.e. aligned generally in the same direction. This orientation may be further illustrated by considering individual fibers to be surrounded by a circumscribing envelope or cylinder; the mean axes of these envelopes are substantially parellelized. The average angle formed by such axes with the plane of a face of the sheet should be at least 10 and, more commonly, essentially 90. By virtue of the crimped, substantially parallelized arrange ment of the fibers, they overlap one another; that is, in at least one view, a fiber crosses over, with or without touching or attachments, an adjacent fiber. As a consequence the fibers are said to coact in that the crimp and relative placement of the fibers are such that they assist one another in producing and maintaining the generally parallelized character both with respect to the general alignment of the fibers and their spacing with respect to each other.

The fibrous structures as described in the aforemen tioned Koller patent can be prepared by a method which comprises forming a plurality of bodies containing substantially parallelized fibers, either per se or in the form of other suitable filamentary structures, placing the bodies in a mold and forming a block while keeping the fibers substantially parallelized, impregnating the block with a binder composition, curing or otherwise solidifying the binder, and cutting the resulting block to a desired shape. Such a block can then be cut at an angle of at least to the plane of orientation of the fibers to obtain a porous, self-supporting material in the form of a sheet structure.

The self-supporting fiber-on-end structures to be treated in accordance with the present invention may have fiber densities upwards from about 0.4 pound/ft. (6.4 kg./ m. but preferably below 6 pounds/ft. (96 kg./m. The fiber density reported in pounds per cubic foot is a measure of the density of the fibers in the article per se, e.g. exclusive of any further layers or material with which the article might be combined. It is calculated by dividing the effective pile weight of the fibers in the article by the volume these fibers occupy when the specimen is under a barely perceptible load, e.g. of 0.01 p.s.i. (0.7 gm./cm. The volume in turn is determined by multiplying the average width by the average length of the conditioned specimen by the effective height, and then applying suitable conversion factors to obtain the volume in units of cubic feet. In addition to expanding the fiber-on-end (i.e. the faces of the sheet being composed essentially of fiber ends) structures already described, the invention may be used for expanding porous flexible, self-supporting sheets in which the fiber orientation is essentially parallel to the faces of the sheet or randomly oriented.

The initial crimped fiber to be used in preparing the bonded fiber structures may be in any of a variety of forms, for example, carded webs of substantially aligned staple fibers or bodies of substantially aligned filamentary structures prepared from a warp of silver, top, roping, roving, tow, stuffer box crimped tow, steam bulked tow, steam crimped continous filament yarn, gear crimped continuous filament yarn, twist set-back twisted continuous filament yarn, knife edge crimped continuous filament yarn, two-component bulky continuous filament yarn, spun yarns and many others. Widely differing types of crimp configurations can be imparted to the fibers. Fibers of either two dimensional or three dimensional crimp or combinations thereof can be employed. For example the irregular contortion can be in the form of crimp, e.g., V-shaped, spiral, loopy, zig-zag, sinusoidal, serpentine, multi-cusped, cycloidal, serrated, or any other form of crimp. The irregularity may be in the form of intermitent pronounced protuberances or thickenings along the length of the structure, e.g., flocked-yarns, thick-and-thin yarns (e.g., such as those in US. 2,975, 474), fuzzy yarns, twisted filaments with fins, twisted ribbon filaments, twisted crescent filaments, twisted elliptical filaments, twisted trilobal filaments, twisted tetralobal filaments, twisted pentalobal filaments, and the like.

In preparing a bonded fiber structure a wide variety of synthetic organic polymeric compositions may be employed. Typical of the fibers and filaments which may be employed are those made of polyamides, such as poly(hexamethylene adipamide), poly(metaphenylene isophthalamide), poly(hexamethylene sebacamide), polycaproamide, copolyamides and irradiation grafted polyamides, polyesters and copolyesters such as condensation products of ethylene glycol with terephthalic acid, ethylene glycol with a 90/10 mixture of terephthalic/isophthalic acids, ethylene glycol with a 98/2 mixture of terephthalic/S-(sodium sulfo)-isophthalic acids, and trans-p-hexahydroxylylene glycol with terephthalic acid, self-elongating ethylenetere hthalate polymers, polyhydroxypivalic acid, polyacrylonitrile, copolymers of acrylonitrile with other monomers such as vinyl acetate, vinyl chloride, methyl acrylate, vinyl pyridine, sodium styrene sulfonate, terpolymers of acrylonitrile/methylacrylate/sodium styrene sulfonate made in accordance with U.S. Pat. 2,837,501, vinyl and vinylidine polymers and copolymers, polycarbonates, polyacetals, polyethers, polyurethanes such as segmented polymers described in US. Pats. 2,957,852 and 2,929,804, polyesteramides, polysulfonamides, polyethylenes, polypropylenes, fluorinated and/or chlorinated ethylene polymers and copolymers (e.g. polytetrafiuoroethylene, polytrifiuorochloroethylene), certain cellulose derivatives, such as cellulose acetate, cellulose triacetate, composite filaments such as, for example, a sheath of polyamide around a core of polyester as described in US. Pat. 3,038,236 and selfcrimped composite filaments, such as, two acrylonitrile polymers differing in ionizable group content cospun side by side as described in US. Pat. 3,038,237, and the like. Blends of two or more synthetic organic fibers may be used, as well as blends of a major weight proportion of synthetic fibers with a minor weight proportion of natural fibers, e.g. silk, wool, cotton, mohair, angora and vicuna. The denier of the fibers of filaments can vary from about 1 to about 50 denier per filament but preferably is below 12 d.p.f.

For purposes of bonding the fibers together throughout the structure the use of a binder composition is preferred over other techniques such as fusion and solvent coalescence. In general the amount of binder composition to be employed in forming a suitable bonded fiber structure will be an amount sufficient to point bond the fibers in the structure to provide a self-supporting material. The maximum quantity of binder in the structure should generally not exceed the quantity of fiber therein, since amounts in excess thereof tend to make the final products excessively rigid. Preferably the binder density will be between 5 and of the fiber density in a given structure. Irrespective of the proportionate quantity of binder composition, it should be distributed substantially uniformly throughout the structure.

The nature of the binder composition employed to interconnect the fibers at a plurality of contact points along their length throughout the three dimensions of the structure can vary widely. Depending upon the use desired these may be either soluble or insoluble, and may be either thermoplastic in nature or may be thermosetting, e.g. as having been produced by the application of a curable composition followed by treatment with a curing agent, a catalyst, heat, etc. If it is desired to remove the binder, a soluble binder will be employed which may be either organic-soluble or water-soluble. Suitable organic-soluble binders include natural rubber or synthetic elastomers (e.g., chloroprene, butadienestyrene copolymers, butadiene-acrylonitrile copolymers), which may be used in the form of a latex dispersion or emulsion or in the form of a solution, vinyl acetate polymers and copolymers, acrylic polymers and copolymers such a polymers of ethyl acrylate, methyl acrylate, butyl acrylate, methyl methacrylate, acrylic acid/acrylic and methacrylic ester copolymers, cellulose nitrate, cellulose acetate, cellulose triacetate, polyester resins such as ethylene terephthalate/ethylene isophthalate copolymers, polyurethanes such as the polymer from piperazine and ethylene bis-chloroformate, polyamide polymers, and copolymers, methoxymethyl polyamides, vinyl chloride polymers and copolymers such as vinyl chloride/vinylidene chloride copolymers latices. Alcohol soluble polyamide resins are also suitable organic-soluble binders. Suitable water-soluble binders include materials such as polyvinyl alcohol, sodium alginate, acrylic acid polymers and copolymers such as polyacrylic acid, carboxymethyl cellulose, hydroxyethyl cellulose, dextrins, animal glue, soybean glue and sodium silicate. Suitable binders which are insoluble in organic solvent include polytetrafluoro ethylene and ureaformaldehyde resin latices.

Additional suitable binder compositions include chlorosulfonated polyethylene; butyl rubbers, such as isobutylene/isoprene copolymers; polyhydrocarbons, such as polyethylene, polypropylene and the like and copolymers thereof; high molecular weight polyethylene glycols sold under the trade name of Polyox; epoxide resins, such as the curable epichlorohydrin reaction products with bisphenols and glycols; polystyrene; alkyd resins, such as polyesters of glycerol with phthalic or maleic acid; polyester resins such as from propylene glycol-maleic anhydride-styrene; phenol-formaldehyde resins; resorcinol-formaldehyde resins; polyvinyl acetals, such as polyvinyl butyral and polyvinyl formal; polyvinyl ethers, such as polyvinyl isobutyl ether; starch, zein, casein, gelatine, methyl cellulose, ethyl cellulose, polyvinyl fluoride, natural gums, polyisobutylene, shellac, terpene resins and resin soaps. Segmented polymers, such as spandex polymers, polyether amides, polyether urethanes (e.g., those in US. 2,929,800) and polyester/urethanes are also suitable.

DRAWINGS The process of the invention will be further described With reference to FIGS. 1, 2, 3, 4, 5, a, 6, and 7.

FIG. 1 illustrates schematically a process for the single stage expansion of a self-supporting fiber-on-end sheet structure and lamination to a backing material.

FIG. 2 schematically illustrates a process similar to that of FIG. 1 excepting that a multiple stage expansion is employed.

FIG. '3 schematically shows a variation of the transfer method of FIGS. 1 and 2.

FIG. 4 is a longitudinal section illustrating one position of the card wires when inserted in a porous fibrous sheet.

FIG. 5 illustrates schematically a modification of the process wherein a comb is used in removing the card wires from the expanded porous sheet.

FIG. 5a illustrates a plan view of the top of the comb shown in FIG. 5.

FIG. 6 illustrates a lamination operation in which an adhesive coating on a porous sheet is melted and the sheet expanded in the longitudinal direction prior to engagement with a fabric.

FIG. 7 illustrates an alternative transfer technique.

The arrangement of FIG. 1 employs a continuous belt of card clothing 12. which is passed over rolls 16, and 17, the larger roll 16 being employed to drive and tension the belt and the smaller roll 17 serving to flex the belt. The card wires 10 are fine (preferably 0.010 (0.025 cm.) inch diameter), long (preferably extending 0.25 inch (0.635 cm.) or greater above the flexible support layer 11), pointed, closely spaced (preferably 600 or more per square inch or 93 or more per square cm.) and inclined backward relative to the sheet travel direction of an angle of 70 with respect to support layer 11. A continuous, porous, fibrous sheet 13 is pressed onto the card clothing wires 10 by means of a feed roll 20 aided by a support roll 21 on the opposite side of the belt. A slight overfeed facilitates penetration of the wires almost completely through the thickness of the sheet to a uniform depth. The sheet 13, supported and internally reinforced by the card wires 10, is then coated on the outer face by spraying an adhesive 22 thereon. The sheet 13 is being meanwhile expanded as it passes through an arcuate path created around the small roll 17. The expansion is precisely controlled by the natural separation and divergence of the wire tips in response to the flex caused by the roll 17. The ratio of the initial longitudinal dimension of the sheet to its final longitudinal dimension being the approximate ratio of the roll radius to the roll radius plus wire length. Of course it will be understood that this is not precise as some slight compression may occur in the support layer 11.While the sheet 13 is still on the flexed card clothing wires 10, a backing fabric 23 is pressed by means of press roll 24 against the adhesive coated surface of sheet 13 to bring about a bond between the backing fabric 23 and the adhesive side of the sheet 13. The composite assembly so formed is then removed from the card clothing. Here the backward pitch of the Wires 10 facilitates this removal because the surface speed of the wire ends slows down at the point that the belt departs tangentially from the roll 17. A thin coating of polytetrafiuoroethylene resin on the wires assist in preventing adhesive from adhering thereto and being withdrawn into the sheet. The adhesive sprayed onto the sheet is chosen preferably such that it will set or solidify almost instantly by cooling or solvent evaporation. For some purposes, however, the adhesive may be one that is tacky or requires curing before setting.

FIG. 2 illustrates a multiple stage expansion process according to the invention. Separate card clothings 12, 12a, and 12b in conjunction with roll 17, 17a, and 17b serve the same expansion function as described with reference to FIG. 1, the difference being that for multiple expansion, two or more card clothing members perfrom a progressive expansion. In FIG. 2, the surface speed of the transmitting card clothing 12 at each point of transfer is slightly greater (e.g., 10% greater) than the surface speed of the receiving belt 12a, the speeds being measured at the tips of the wires. This diflerential in conjunction with the backward slant of both sets of wires 10 and 10a causes the second set of wires to engage the sheet 13 and disengage it from the first" set of wires. After being expanded a second time in a similar manner by means of card clothing 12b, the wafer may be flexed again and adhered to a backing as shown in connection with FIG. 1.

FIG. 3 illustrates an alternative, but preferred, transfer technique for use in a single or multiple stage expansion process. In this arrangement an open web 31 such as a loosely constructed nylon warp of parallel monofilament or multifilament strands, a wire warp, a scrim fabric, or other material is used in conjunction with a filler 32 between the lower portions of the wires to limit the degree of penetration into the sheet. The filler 32 may be a soft plastic foam or other material which is at least elastic in the longitudinal direction. Such an elastic material will thus serve as a base to keep the open web 31 snugly against the undersurface of the sheet 13. Alternatively the card clothing filler 32 may comprise a generally inelastic material which is transversely severed into sections between the card wires. A typical open web member for use in this technique is a 300 denier nylon monofil warp having twelve strands per inch of width. A guide roll 33 at each point of sheet transfer causes the warp strands to leave the transmitting belt on a tangential path, forcing the sheet to exchange engagement from one set of card clothing to the second set of card clothing. The open web 31 is separated from the sheet by means of roll 33. The advantage of this transfer system is that the two belts may have identical surface speeds at the transfer point, thereby minimizing fiber disturbances in the sheet being expanded. Also, because longer wires can be used which are nevertheless supported at their bases by the filler, the wire tips are spread further and permit an increase in the degree of expansion of the sheet.

FIGS. 5 and 5a illustrate an alternate preferred meth 0d of transfer. A continuous belt of card clothing 12 with support layer 11 is passed over, and departs tangentially from roll 17. A continuous porous fibrous sheet 13 is pressed onto the card clothing wires 10 and is then transferred to roll 24. Comb 35 is located at the point of transfer in a manner such that the tines 36 of comb 35 pass between the rows of the wires 10 of card cloth 12. The tines 36 are preferably tapered steel blades. The pointed extremities of the tines 36 are below the level that sheet 13 engages wires 10. The face of the comb 35 makes a slight angle with the belt tangent at the tips of the wires 10 so that advancement of sheet 13 by the card cloth 12 causes the sheet 13 to move along the face of the comb and away from the card cloth 12. The comb 35 is taped and due to the forward movement of the sheet 13 provides a force on the underside of the sheet which lifts it and cases it off the wires 10. If a second card cloth conveyor is employed, the comb 35 is so positioned in relation to it that its movement forces the sheet 13 into engagement with the second hOlding means.

FIG. 6 illustrates a lamination operation in which an adhesive coating on a porous sheet is melted and the sheet expanded in the longitudinal direction prior to engagement with a fabric. Sheet 13 and open web 31 are fed onto card clothing 12 supporting wires 10. Fabric 23 is fed by press roll 24 into engagement with sheet 13 after an adhesive on the top surface of 13 has been melted by heat from radiator 37 and sheet 13 has been expanded by flexure around roll 17. The fabric and sheet becomes attached in the engagement and are released from wires by open web 31 which is guided away from roll 17 by passage around roll 33.

FIG. 7 illustrates an alternative transfer technique. Card clothing belts 12 and 12a are flexed in passage around rolls 17 and 17a respectively. The clothings have wires 10 and 10a for engagement of porous sheet 13. Clothing 12a is given a path of travel which brings wires 10a into engagement with sheet 13 after the sheet has been expanded by the flexure around roll 17. Clothing 12a is straight and running at a slower speed than the peripheral speed of wires 10 at this point, this speed difference causing the sheet to leave wires 10 and be carried forward by clothing 12a. A commercial grade of adhesive coated masking tape 38 thereafter is brought into contact with sheet 13 to effect an adhesion permitting the sheet to be removed from wires 10 without any additional change in the surface dimensions of the sheet.

When two or more belts of card clothing are employed in a multiple stage expansion, a lamination can be carried out simultaneously as the sheet is flexed and expanded. Alternatively, the lamination can occur later so long as an appreciable amount of the exansion is preserved. For example the lamination can take place as the sheet passes through a linear path on a card clothing belt. In this case the belt could be of sufficient length to provide time for curing the laminating adhesive. The utilization of the card clothing as a support during lamination makes possible the application of pressure to the interior of the sheet. In this way any tendency for the sheet to undergo a loss in thickness can be minimized.

The setting of the expanded self-supporting fiber-onend sheet structure can be accomplished in a variety of ways. A preferred way, involving spraying the sheet with adhesive and lamination to a backing material, is illustrated in FIG. 1. Rather than applying adhesive in such a manner during the flexing process, however, it may also be initially provided upon the fiber-on-end sheet or upon the backing layer or both. For this purpose it may be normally tacky polymer which requires heat to harden or cure, or it may be a substance which is rendered tacky by heating during the flexing and lamination step. In either case, depending upon the extent to which the sheet will tend to return to its original unexpanded condition, i.e. depending upon its relative elasticity, it may be desirable for the backing material to be relatively inflexible and inelastic so as to overcome that tendency and thereby prevent the laminate from curling up.

Whether or not the sheet is to be laminated to one or more backing materials, it is also possible to heat-set the sheet in the expanded condition. Thus when a binder composition is used that comprises a thermoplastic material melting below the fiber softening point, this may be accomplished by heating to soften the binder and hence effectively create fiber-to-fiber bond points which are under a reduced amount of stress. Alternatively, the fibers of the sheet may be heat-set to retain the expanded condition by heating to a temperature above the second order transition temperature of the fibers followed by cooling. It will be apparent that for those applications requiring the adherence of a backing material to both sheet faces, e.g. in sandwich fashion, there will be a reduced tendency for the sheet to return to its initial unexpanded condition even without special treatment.

Expanded sheet products not requiring lamination to a backing layer can also be set in the expanded state by application of a surface film of plastic or the like or by introducing and curing a binder prior to release from the card clothing. An expanded sheet will also attain a set condition if it has been extended in an extreme radius flex and then forced or allowed to return to an intermediate state of expansion. Stress relief in this manner may also be carried out when the product is to be laminated or simply coated with an adhesive film.

EXAMPLES The invention will be further described in the examples which follow. All parts therein are by weight unless otherwise indicated.

In Examples 1-6 certain porous blocks are employed from which thin sheets are sliced parallel to the faces of the block containing the majority of fiber ends. Block A is made from a blend of staple fibers of ethylene terephthalate polymer having a three-dimensional helical crimp (Kilian US. Patent 3,050,821), 4 denier per filament and a staple length of 2 inches (5.08 cm.). which are carded into a web with staple fibres of ethylene terephthalate polymer having a stuifer-box type of crimp, 1.5 denier per filament and a staple length of 1.5 inches (3.8 cm.). The final ratio of the staple fibers in the blend is 60/40 parts respectively, by weight. The weight of the web is 66.5 grains per foot (2.2/crn.). The web is rolled into a sliver and a sheet of 32 end of this sliver is fed into a perforated mold having a depth of 18 inches (45.7 cm.). The sheet of slivers is given a vertical orientation across the 94 inch (238 cm.) dimension. The sheet is then cut and pressed to a inch (1.79 cm.) dimension in the length dimension of the mold, this length being 112 inches (284 cm.). Additional loadings of the sheet are made until the entire mold is filled with 66 pounds (29.9 kg.) of fiber. The mold is then covered with a perforated plate and dipped into a tank containing a 4% by weight binder solution in trichloroethylene solvent of a heat curable polyurethane formed of 2,4-toluene diisocyanate and a polyester of ethylene glycol and adipic acid. The mold is then withdrawn from the tank and allowed to drain for one hour. The mold is placed in an oven at 240 F. and the urethane cured. The final weight of the block upon removal from the mold is 74.25 pounds (33.7 kg).

EXAMPLE 1 A thin porous sheet having a thickness of inch (0.32 cm.) is sliced from block A with the fibers oriented generally in the same direction with their ends in the two faces of the block. The porous sheet has a fiber density of 0.7 lb./ft. (11.2 kg./In. This sheet is expanded 35% in the longitudinal dimension in a machine equipped with a continuous card clothing belt, such as is shown in FIG. 6. One face of the sheet in this example contained a one ounce per square yard (.034 kg./m. coating of polyester adhesive. The composition of the adhesive is:

Grams Reaction product of a 1.6:1.0 molar ratio of 2,4-

toluene diisocyanate and polytetrarnethylene ether glycol (M.W.=1000) a Acetone 100 Particulate silica (anhydrous colloidal) 10 The continuous belt is 40 inches wide (101.6 cm.) and approximately 36 inches long (91 cm.). Card wires of .010 inch (.025 cm.) diameter projected from the surface of the belt a distance of inch (.635 cm.) measured normal to the surface. Each wire has a bend at inch (.16 cm.) from the surface giving a backward angulation of 70 with the surface. The density of the Wires is 720 per square inch (112/cm?) and each wire is ground to a sharp tip. The belt proper has six plys of cotton fabric and a base ply of rubberized nylon tire cord placed in the lengthwise direction. The total thick- 1 1 ne-ss of the belt is approximately 4; inch (.317 cm.). The wires in the form of staples passed through the cotton plys but not the nylon ply. The belt is driven at a speed of 5 inches (12.7 cm.) per minute by a drive roll (not shown in FIG. 6) and is flexed around a 1 /2 inch (3.8 cm.) diameter idling roll.

The sheet is continuously fed onto the moving belt and pressed into the card cloth covering to a depth of one half the sheet thickness. It passed under a radiant heater having a surface of 1000 F. The adhesive surface on the sheet was uppermost and the adhesive is melted before the flex roll 17a was reached. A wool backing fabric of crepe weave and 5.4 oz. per square yard (183 gn1./m. weight is fed by a 4 /2 inch (11.4 cm.) diameter roll driven at 6.75 feet (2.06 m.) per minute under a portion of the same heater and into contact with the Sheet at a point of maximum sheet fiexure. A warp sheet of 330 denier nylon monofilament, having 12 filaments per inch (4.7/cm.) of belt width, traveled with the belt between the wires. The warp sheet is fed onto the card clothing before the porous sheet is engaged, and the filaments of the warp sheet caused to rest at the base of the clothing wires. Immediately after the slight pres sure contact is made between the backing and the sheet, the monofilaments are guided away from the flex roll, thereby forcing the sheet to leave the card clothing and adhere to the backing. The 35 expansion in the longitudinal dimension of the sheet is achieved, thereby reducing the fiber density.

The resulting laminate is uniform and of good appearance. There is no noticeable loss in sheet thickness. The product manifested good bulk, body and drape and is considered useful for ladies suits.

EXAMPLE 2 A porous fiber-on-end block made with a melamine/ formaldehyde binder composition is sliced into a sheet having a thickness of 3 inch (.24 cm.) and this sheet is expanded under the identical conditions used in Example l, except that no backing fabric is used and no surface adhesive on the face of the sheet. The same radiant heater as used in Example 1 served to heat set the porous sheet in the stretching zone, so the resulting Stretched product having 35% longitudinal expansion is stable to dimensional change. The binder composition is a butylated melamine/ formaldehyde resin. The amount of binder used is 7% based on the weight of fiber. The fiber density of the sheet is 1 lb./ft. (16 kg./m. The resulting expanded sheet is stable to dimensional change 'upon processing on textile machinery.

EXAMPLE 3 A porous sheet having a thickness of 7 inch (.24 cm.) and a fiber density of 1 lb./ft. (16 kg./m. is expanded 100% in its longitudinal dimension by three passes through the same apparatus used in Example 2. The conditions are identical for the three passes and the expanded sheet is heat set by exposure to a radiant heater having a surface temperature of 1000 F. This stablizes the dimensions of the expanded sheet Without the aid of an adhesive or a laminating fabric. The sheet employed is sliced from a block perpendicular to the fiber direction, containing the same quantity of melamine/formaldehyde resin binder as used in Example 2, and the porous block is prepared in the same manner as in Example 2. The resulting expanded product has good uniformity and manifested no loss in thickness. Considering the low final fiber density of 0.5 lb./ft. (8 kg./m. the sheet has surprisingly good cover and bulk and is considered useful as a garment lining material.

EXAMPLE 4 A porous fiber-on-end block is made as in Example 1, using by weight of urethane binder based on the fiber weight to yield a block having a fiber density of 12 4 lbs./ft. (64 kg./m. The fiber used in making the block is 100% polyethylene terephthalate staple fiber [4 d.p.f., 2 inch (5.1 cm.) length] having a helical crimp which is described in Kilian US. Pat. 3,050,821. A

- sheet of 0.25 inch (.63 cm.) thickness is sliced from the block and expanded 100% in length by three passes through the apparatus used in Example 2.

EXAMPLE 5 A block is prepared as in Example 1 and using the same compositions, but a fiber density of 1.25 lbs/ft. (20 kg./m. A sheet of the same thickness is sliced from the block and without surface adhesive is expanded 50% in length by employing part of the apparatus shown in FIG. 2. The card clothing belt coverings has 624 wire points per square inch (97/cm. The wires of 37 gauge [0.0085 inch (.022 cm.)] extend 0.25 inch (.63 cm.) above the card clothing foundation and are angled without any bends. Automatic transfer from card clothing 12 to 12a is affected by having a straight portion of clothing 12a travel at a speed 10% less than the peripheral speed of clothing 12 at the point of joint engagement and maximum flexure of the clothing 12. The diameter of the flex roll 17 is 1.25 inches (3.2 cm.). The expanded sheet is stabilized on card clothing 12a without the use of heat by engagement with a commercial grade of adhesivecoated masking tape applied'by hand (not illustrated) before the sheet reaches the provision for the second expansion in FIG. 2. The sheet is then stripped from the clothing wire 12a by means of the tape and retained the full amount of the expansion.

EXAMPLE 6 A block is prepared following the procedure given for the block used in Example 1, except that 100% of polyester fiber having a helical crimp, 4 d.p.f. and 2 inch (5.1 cm.) staple length is employed using a mold measuring 10 inches by 40 inches by 48 inches (25.4 x 101.6 x 121.9 cm.). The binder used is 4.7% based on the fiber weight. The fiber density in the final block is 1.25 lbs/ft. (20 kg./n1. The binder composition is a heat curable polyurethane formed of 2,4-toluene diisocyanate and a polyester of ethylene glycol and adipic acid.

A sheet having a thickness of :2 inch (.24 cm.) is sliced from the block perpendicular to the fiber direction. No adhesive is added directly to the surface of the sheet. The sheet is expanded 228% longitudinally in a single step and fixed at 3.28 times its original length without sacrifice in the other dimensions using the equipment shown in FIG. 7. The card clothing has 234 points per square inch (36.3/cm-. of 0.018 inch (.046 cm.) diameter wire. The wires extend inch (1.35 cm.) above the 0.105 inch (.27 cm.) thick, 4-ply cotton foundation and each wire is bent 0.25 inch (.63 cm.) above the foundation to a backward inclination of 65. Flexure took place around a bar having a radius of inch (.48 cm.). The sheet is pressed onto the card wire to approximately 75% of the sheet thickness. The sheet is fixed in the expanded state by engagement at a point of maximum flexure with a commercial tape having pressure sensitive adhesive coating. The tape also served in stripping the sheet from the card clothing. The resulting expanded sheet product manifests good continuity of the sheet surface and a surprising amount of bulkand load support for the 0.38 lb./ft. (6.1 kg./m. fiber density.

EXAMPLE 7 This example illustrates the use of the invention for self-supporting sheet structures other than fiber-on-end construction.

Polyethylene terephthalate staple fiber having a three dimensional helical crimp is prepared according to Kilian US. Pat. 3,050,821. The fiber is carded into a commercially available inch thick self-supporting fibrous sheet with the fiber in the sheet oriented predominantly in the lengthwise direction (i.e., the fiber is essentially parallel to the faces of the sheet). The sheet has a 0.63 lbs/ft. total density with a 18% acrylic resin (by weight) sprayed on the two faces (surfaces). The sheet is slit to an approximate /s inch thick wafer with the resin predominantly on one side. This side is pressed onto a 1 /2 inch wide strip of card clothing having 720 points of 0.010 inch wire per square inch projections 7 inch above a X inch backing fabric. The wires are bent backward 70 at a point 7 inch above the base fabric. The card clothing with the sheet on it is flexed around a 1 inch diameter rod and removed from the card clothing at a point of maximum flexure with a commercial masking tape that stabilized the expansion.

The product has good appearance and measured markings show a 44% expansion in the longitudinal direction.

The invention has been described in detail with reference to various preferred embodiments. Numerous modifications and other embodiments will be apparent to those skilled in the art without departing fromthe spirit of the invention or the scope of the claims which follow.

What is claimed is:

1. Method for reducing the fiber density and expanding the face dimensions of a porous flexible, self-supporting sheet composed of substantially parallelized, crimped, synthetic organic, polymeric fibers which are attached at a plurality of contact points throughout the three dimensions of said sheet, the air within said sheet constituting at least about 50% of its volume; said method comprising the steps of (1) penetrating said sheet to a predetermined distance with a multitude of elongated projecting elements extending from a flexible support layer (2) flexing said sheet upon said flexible support layer to spread apart the elongated projecting elements and thereby expand the face dimensions of said sheet, and (3) setting said sheet in the expanded condition and removing the elongated projecting elements therefrom.

2. Method of claim 1 wherein said sheet is set in the expanded condition by adhering the larger face thereof to a backing material.

3. Method of claim 1 wherein the elongated projecting elements extend through at least one-fourth the thickness dimension of said sheet and are provided at a density of at least 300 per square inch.

4. Method of claim 1 wherein said fibers are attached by a binder composition.

5. Method of claim 1 wherein the faces of said sheet are composed essentially of fiber ends and said sheet is penetrated by said elongated projecting elements with said elongated projecting elements extending into said sheet in general alignment with said fiber.

6. Method for reducing the fiber density and expanding the face dimensions of a porous flexible, self-supporting sheet composed of substantially parallelized, crimped, synthetic organic, polymeric fibers which are attached at a plurality of contact points throughout the three dimensions of said sheet, the faces of said sheet being composed essentially of fiber ends and the air within said sheet constituting at least about of its volume; said method comprising penetrating said sheet to a predetermined distance with a multitude of elongated projecting elements extending from a flexible support layer, moving said sheet upon said flexible support layer along an arcuate path whereby said elongated projecting elements become spread apart in the direction of said path to thereby expand the dimensions of the sheet faces, and adhering the expanded sheet to a backing.

7. Method of claim 6 wherein said arcuate path is formed by rotation of the sheet upon said flexible support layer about a roll.

8. Method of claim 7 wherein said backing is pressed into contact with said outer sheet face as it reaches a maximum state of expansion about said roll.

9. Method of claim 8 wherein said backing is provided with an adhesive composition.

10. Method of claim 8 wherein an adhesive composition is contained on said outer sheet face.

11. Method of claim 7 wherein said elongated projecting elements comprise a generally uniform distribution of small diameter wires extending from said flexible support layer.

12. Method of claim 11 wherein said wires are embedded to at least half the thickness dimension of said sheet.

13. Method of claim 7 wherein the face dimensions of said sheet are expanded at least 20% in length.

References Cited UNITED STATES PATENTS 2,675,337 4/1954 Walker et al. 156164 CARL D. QUARFORTH, Primary Examiner B. H. HUNT, Assistant Examiner 

